1. Field of the Invention
This invention relates to a system for removing particles from exhaust produced by internal combustion engines, such as diesel engines.
2. Description of the Prior Art
Exhaust produced by diesel engines has a relatively high content of polluting particles composed of carbon, unburned fuel, and partially burned fuel. Filters or traps are conventionally disposed in engine exhaust systems to remove the particles from the exhaust. In this case, burners positioned in the exhaust systems upstream of the filters are usually employed to burn off particles deposited on the filters to unclog and rejuvenate the filters.
Japanese published patent applications 54-12029 and 56-115809, and Japanese utility model application 56-22107 (publication number 57-136814) disclose such burners. Burning the fuel supplied to these burners uses oxygen contained in the exhaust. Under heavy engine load conditions, the oxygen concentration in the exhaust may be inadequate to completely burn the supplied fuel. If the burners are activated under such engine operating conditions, a large amount of unburned fuel can, therefore, be discharged into the atmosphere.